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HDI Stack Up

Joseph Ogbonna , 04-27-2024, 11:54 AM
Is this stack up ok for my HDI Design.
8 Layers

1 - Sig
2 - Gnd
3 - Sig
4 - Pwr
5 - Gnd
6 - Pwr
7 - Gnd
8 - Sig

Am using RK3399 chip from Rock chip for the design. About 800 pins.
BGA pitch 0.65mm
@Robert Feranec

Planning on using 2+N+2
Joseph Ogbonna , 04-27-2024, 11:55 AM
You can give me a recommendation if any. Thanks
QDrives , 04-27-2024, 03:31 PM
Components on both sides?
Just a thought on my end, but would power on an outer layer (ie bottom) be better as the plating makes it thicker and thus it can carry more current?
Sniper2 , 04-27-2024, 03:33 PM
is it for work?
Sniper2 , 04-27-2024, 03:33 PM
asking since i was thinking of useing that chip but i did not find it at part retailers
Robert Feranec , 04-28-2024, 05:26 AM
I do not normally use 8 layer stackup as it is not very optimal. for example in this case I keep thinking about distances between layer 3-4-5-6, their specific construction (if prepreg is going to be used or core) and if layer 4 is going to be reference layer for layer 3. However, the board will probably work just fine even if the stackup is not perfect ... I am just thinking if this could be somehow improved or what to be careful about, the biggest thoughts go to layer 4 but I don't have any specific ideas what to do with it, because powerplane used as reference plane may sometimes be tricky or not the most optimal.
Sniper2 , 04-28-2024, 04:12 PM
so effectively you advise him to use a 10 layer stackup ?
Robert Feranec , 04-28-2024, 04:57 PM
I don't know what is on the board, but for CPU boards often 4 signal layers are needed. however 10 layer will be more expensive
Joseph Ogbonna , 04-28-2024, 07:52 PM
So what's the best stack. The board contains PCIe, USB highspeed, MiPi CSI and DSI, EMMC, two LPDDR3 1G each.
Joseph Ogbonna , 04-28-2024, 07:54 PM
Am actually trying to design the board so I can get conversant with HDI Design principles, am not producing it. Needed guide on best HDI Stack Up
Robert Feranec , 04-29-2024, 05:56 AM
two LPDDR3: that is why I said you may need 4 signal layers. Just to be sure, does reference board have it routed on 3 signal layers?
Joseph Ogbonna , 04-30-2024, 05:56 AM
Yes reference board has 3 signal layer, but the route is kind of congested
Joseph Ogbonna , 04-30-2024, 05:56 AM
I think I will make it 10 layers instead
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